In particular, electronically regulated vehicle brake systems have a hydraulic assembly comprising a receiving body with electrohydraulic valves, with at least one hydraulic pump, and with channels for connecting the pump to at least one hydraulic consumer, a pulsation damping unit being provided between a pressure medium volume (THZ/container, low pressure accumulator) and a suction side of the pump or between a pressure side of the pump and the hydraulic consumer. Eccentric-driven radial piston pumps are mostly used. Millions of said hydraulic assemblies are in use.
Each piston displacement during an eccentric revolution can be divided in an extremely simplified manner into a suction stroke (0−n) and into a pressure stroke (n−2n). Because in each case liquid columns are accelerated but also retarded, this leads on the suction side and also on the pressure side to largely sinusoidal instantaneous pressure profiles which can be changed in details as a function of the concrete embodiment or else can be superimposed. In order to compensate for undesired effects of the instantaneous pressure profiles which fluctuate because of their principle, a pulsation damping unit is provided.
For example, it is known from DE 34 14 558, which is incorporated by reference, to use a diaphragm damper with a metal diaphragm for pulsation damping. Conventional diaphragm dampers with a clamped elastomer diaphragm can suffer from the disadvantage that they are subject to wear, with the result that their effect decreases over the length of the service life. The spring properties are dependent on how quickly the loading takes place (dynamic hardening). As a result, they suffer from nonlinear behavior.
DE 10 2005 028 562 A1, which is incorporated by reference, has disclosed a braking hydraulic assembly comprising a hermetically closed metal hollow body for damping purposes.